The present invention relates to a multi-lamp type vehicular headlamp.
A vehicular headlamp is commonly capable of selectively switching between a low-beam light distribution pattern and a high-beam light distribution pattern. It is difficult for a vehicular headlamp having fixed light distribution patterns to produce a beam with a light distribution pattern which is always optimal for the instant operating conditions of the vehicle.
In view of this problem, a vehicular headlamp has been proposed which forms a synthesized light distribution pattern of beams emitted from a plurality of lamp fixture units and wherein at least one of the lamp fixture units is pivoted as appropriate according to the operating conditions of the vehicle (e.g., steering angle and speed) so that a beam can be produced with a synthesized light distribution pattern which varies according to the operating conditions of the vehicle.
FIG. 6 is a front view of a vehicular headlamp 110, which is a specific example of such a vehicular headlamp, and FIG. 7 is a perspective view of a synthesized light distribution pattern that is emitted ahead of the vehicle from the vehicular headlamp 110 while the vehicle is turning left.
As shown in these two drawings, the vehicular headlamp 110 has a headlamp unit 116 for emitting a low beam with a basic light distribution pattern Pxe2x80x2 having a horizontal cutoff line CL1xe2x80x2 and an oblique cutoff line CL2xe2x80x2, and a pair of auxiliary lamp fixture units 118, 120 for emitting beams with respective auxiliary light distribution patterns P1xe2x80x2, P2xe2x80x2 that partially reinforce the brightness of the basic light distribution pattern Pxe2x80x2. By pivoting the auxiliary lamp fixture units 118, 120 about respective vertical axes A1xe2x80x2, A2xe2x80x2 to move the auxiliary light distribution patterns P1xe2x80x2, P2xe2x80x2 as appropriate in the horizontal direction, the vehicular headlamp 110 will provide a beam with a synthesized light distribution pattern which varies according to the operating conditions of the vehicle.
However, this vehicular headlamp 110 has certain problems. For example, as shown in FIG. 7, when the auxiliary light distribution pattern P2xe2x80x2 formed under the oblique cutoff line CL2xe2x80x2 moves away from the center of the basic light distribution pattern Pxe2x80x2 to form a pattern P2xe2x80x3, the hot zone HZxe2x80x2 of the basic light distribution pattern Pxe2x80x2 and the hot zone HZ2xe2x80x2 of the auxiliary light distribution pattern P2xe2x80x3 become separated from each other. As a result, the road surface ahead of the vehicle becomes relatively dark in the region between the hot zones HZxe2x80x2, HZ2xe2x80x2 due to contrast with the hot zones HZxe2x80x2, HZ2xe2x80x2, thereby significantly degrading the visibility of that region of the road surface.
The present invention is made in view of the above problem, and it is an object of the present invention to provide a vehicular headlamp capable of moving an auxiliary light distribution pattern in the horizontal direction by pivoting an auxiliary lamp fixture unit and which is capable of effectively suppressing degradation in the visibility of the road surface ahead of the vehicle caused by movement of the auxiliary light distribution pattern.
The present invention achieves the above object by appropriate selection of the pivot direction of the auxiliary lamp fixture unit.
More specifically, a vehicular headlamp according to the present invention includes: a headlamp unit for emitting a beam with a prescribed basic light distribution pattern, and an auxiliary lamp fixture unit for emitting a beam with an auxiliary light distribution pattern that partially reinforces the brightness of the basic light distribution pattern, the auxiliary lamp fixture unit being supported so that it is pivotable about a prescribed pivot axis to move the auxiliary light distribution pattern in a horizontal direction. The above vehicular headlamp is characterized in that the pivot axis is tilted at a prescribed angle with respect to a vertical direction so that the auxiliary light distribution pattern is displaced upward when it is moved away from the center of the basic light distribution pattern.
The headlamp unit and auxiliary lamp fixture unit are not particularly limited in terms of their specific structures. For example, a parabolic lamp fixture unit or a projector-type lamp fixture unit may be employed. Moreover, the light sources of the headlamp unit and auxiliary lamp fixture unit are not particularly limited in terms of their specific structures. For example, a discharge light-emitting portion of a discharge bulb or a filament of an incandescent bulb such as halogen bulb may be employed.
According to the above structure, in the vehicular headlamp of the present invention, the auxiliary lamp fixture unit is supported so that it is pivotable about a prescribed pivot axis to move in the horizontal direction the auxiliary light distribution pattern that is formed by a beam emitted from the auxiliary lamp fixture unit. Moreover, the pivot axis is tilted at a prescribed angle with respect to the vertical direction so that the auxiliary light distribution pattern is displaced upward when moved away from the center of the basic light distribution pattern that is formed by a beam emitted from the headlamp unit. As a result, the following effects can be obtained:
As the auxiliary light distribution pattern is moved away from the center of the basic light distribution pattern, the hot zone of the auxiliary light distribution pattern may be separated away from the hot zone of the basic light distribution pattern. However, since the hot zone of the auxiliary light distribution pattern is displaced upward at this time, the position of this hot zone on the road surface ahead of the vehicle is shifted away from the vehicle. As a result, the illumination intensity of this hot zone on the road surface ahead of the vehicle is reduced sharply. Since the two hot zones do not concurrently reside on both sides of the road surface ahead of the vehicle, the road surface ahead of the vehicle is prevented from becoming relatively dark in the region between the hot zones due to contrast with the hot zones.
Thus, according to the present invention, a vehicular headlamp is realized which is capable of moving the auxiliary light distribution pattern in a horizontal and upward direction by pivoting the auxiliary lamp fixture unit and which therefore effectively significantly reduces any degradation in visibility of the road surface ahead of the vehicle caused by movement of the auxiliary light distribution pattern.
The auxiliary light distribution pattern is moved away from the center of the basic light distribution pattern mainly in order to improve the visibility ahead of the vehicle when the vehicle turns right or left. Displacing the auxiliary distribution pattern upward as in the present invention enables the road surface away from the vehicle to be illuminated, thus causing the visibility of the road surface ahead of the vehicle to be effectively improved.
The basic light distribution pattern is not particularly limited in terms of its specific composition. When the basic light distribution pattern is a low-beam light distribution pattern having a horizontal cutoff line and an oblique cutoff line, a hot zone is formed in a region relatively close to the vehicle on the road surface ahead of the vehicle. It is therefore particularly effective to use the structure of the present invention which is capable of preventing the road surface ahead of the vehicle from becoming relatively dark in the region between the hot zones. In this case, when the auxiliary lamp fixture unit forms the auxiliary light distribution pattern under the oblique cutoff line, the tilt angle of the pivot axis of the auxiliary lamp fixture unit with respect to the vertical direction may be smaller than the angle at which the oblique cutoff line is tilted upward. As a result, the following effects can be obtained:
In the low-beam light distribution pattern having a horizontal cutoff line and an oblique cutoff line, the horizontal cutoff line is formed by horizontally diffused, deflected light from the headlamp unit, and the oblique cutoff line is formed by obliquely diffused, deflected light along the oblique cutoff line from the headlamp unit. Therefore, the region located under the oblique cutoff line and above the horizontal cutoff line and somewhat away from the center of the basic light distribution pattern becomes relatively dark.
The tilt angle of the pivot axis with respect to the vertical direction may be smaller than the angle at which the oblique cutoff line is tilted upward. In this case, the brightness of the relatively dark region (the region located under the oblique cutoff line and above the horizontal cutoff line and offset from the center of the basic light distribution pattern) can be effectively compensated when the auxiliary light distribution pattern is moved away from the center of the basic light distribution pattern. This further improves the visibility ahead of the vehicle when the vehicle turns right or left.
The above-described vehicular headlamp may include as the auxiliary lamp fixture unit a unit corresponding to the horizontal cutoff line for forming the auxiliary light distribution pattern under the horizontal cutoff line and a unit corresponding to the oblique cutoff line for forming the auxiliary light distribution pattern under the oblique cutoff line. This improves the visibility ahead of the vehicle whether the vehicle turns right or left. In such a case, it is desirable in order to prevent glare to the driver of an oncoming vehicle to tilt the pivot axis of the unit corresponding to the horizontal cutoff line at a smaller angle than that of a pivot axis of the unit corresponding to the oblique cutoff line with respect to the vertical direction. More specifically, by setting the tilt angle of the pivot axis of the unit corresponding to the horizontal cutoff line to a relatively small value, the auxiliary light distribution pattern formed by the unit corresponding to the horizontal cutoff line can be prevented from extending excessively upward beyond the horizontal cutoff line when it is moved away from the center of the basic light distribution pattern. This improves the visibility ahead of the vehicle when the vehicle turns right or left, while preventing glare to the driver of an oncoming vehicle.